The present invention relates generally to the use of aci-reductone compounds to improve lymphokine activated killer (LAK) cytotoxicity and to the pharmaceutical use of such aci-reductone compounds in the treatment of cancer.
The invention further relates to a method for improving interleukin-2 (IL-2)-induced lymphocyte-killing of cancer cells in a patient having cancer by administering to a patient having cancer at least one aci-reductone compound containing a --C(OH).dbd.C(OH)--C.dbd.O redox functionality or a physiologically acceptable salt thereof.
It is know that arachidonic acid (AA) metabolites and reactive oxygen species (ROS) suppress interleukin (IL-2) antitumor activity and mediate IL-2 toxicity. The present invention shows that aci-reductones, a family of synthetic compounds which inhibit AA and ROS metabolism, can improve IL-2 antitumor efficacy and lessen IL-2 toxicity.
IL-2 is an important mediator of the immune response. Of particular significance to cancer therapy is the capacity of IL-2 to generate cytotoxic lymphocytes. LAK cells are predominantly IL-2 activated natural killer (NK) cells which are capable of lysing tumors resistant to NK cells.
It is known that incubation of human peripheral blood mononuclear cells (PBMC) with interleukin-2 (IL-2) induces a population of highly tumoricidal lymphocytes. This phenomenon is referred to as LAK activity as described in Rosenburg, Adoptive immunotherapy of cancer using lymphokine activated killer cells and recombinant interleukin-2, in DeVita VT, Hellman S, Rosenberg SA (eds.): Important Advances in Oncology. Philadelphia: Lippincott, 1986, pp. 55-91. The precursor of the effector cells may be heterogeneous, but most of the activity appears to originate from IL-2 activation of natural killer (NK) cells as described in Ortaldo et al., Lymphokine activated killer cells: Analysis of progenitors and effectors. J. Exp. Med. 164:1193, 1986; and Philips et al., Dissection of the lymphokine activated killer phenomenon. J. Exp. Med. 161:814, 1986. IL-2, alone or with the adoptive infusion of LAK cells, has demonstrated antitumor activity in vivo. Although a wide spectrum of tumors are sensitive in vitro, most tumors have not been completely responsive in vivo. The best results in clinical trials have been with melanoma and renal cell carcinoma. Since promising responses have been observed in patients with tumors for which there are no effective chemotherapies, there is considerable interest in developing new IL-2 therapies. However, IL-2 regimens have also been toxic, inducing inflammatory responses such as fever and chills, and the capillary leak syndrome characterized by extravasation of plasma into tissues, hypotension, and multiple organ dysfunction. Most studies suggest that IL-2 toxicity results indirectly though the effects of proinflammatory cytokines such as tumor necrosis factor (TNF) and IL-1.
It is now believed that a number of mediators may be involved in the abrogation of IL-2 antitumor activity and in IL-2 toxicity. Several lines of evidence implicate a role for AA metabolites and ROS, which are both important mediators of the immune responses.
Metabolism of AA is by two basic pathways: (1) the cyclooxygenase pathway which leads to prostaglandin and thromboxane and (2) the lipoxygenase pathway which leads to leukotrienes and lipoxins. Products of both pathways have immunomodulatory effects. ROS having immunodulatory effects include superoxide anion (O.sub.2.sup.-), hydrogen peroxide (H.sub.2 O.sub.2), hydroxyl radical, products of lipid peroxidation, and myeloperoxidase-halide-H.sub.2 O.sub.2 products. The major source of AA metabolites and ROS relevant to cytoxic lymphocyte activity are phagocytes; tumors may also be important sources.
In particular, IL-2 has been shown to induce the production of AA and ROS metabolites as described in Parker et al., Formation of TxB.sub.2 and hydroxyarachidonic acids in purified human lymphocytes in the presence and absence of PHA. J. Immunol. 122:1572, 1979; Remick et al., Stimulation of prostaglandin E.sub.2 and thromboxane B.sub.2 production by human monocytes in response to interleukin-2. Biochem. Biophys. Res. Commun. 147:86, 1987; Bermudez, Tumor necrosis factor, alone or in combination with IL-2, but not IFN-gamma, is associated with macrophage killing of Mycobacterium avium complex, J. Immunol. 140:3006-3013, 1988; Frasier-Scott et al., Influence of natural and recombinant interleukin-2 on endothelial cell arachionate metabolism, J. Clin. Invest. 82:1877-1883, 1988; Tilden et al., Interleukin-2 augmentation of interleukin-l and prostaglandin E.sub.2 production; J. Leuk. Biol. 45:474-478, 1989; Valitutti et al., The expression of functional IL-2 receptor on activated macrophage depends on the stimulus applied, Immunology 67:44-50, 1989; and, Klausner et al., The rapid induction by interleukin-2 of pulmonary microvascular permeability, Ann. Surg. 209:119-128, 1989. The suppressive effects of the cyclooxygenase product of AA, prostaglandin (PG) E.sub.2, on lymphocyte cytotoxicity have been well-established by Chouaib et al., Prostaglandins E as modulators of the immune response, Lymphokine Res. 7:237-245, 1988. Further prostaglandin E.sub.2 (PGE.sub.2) released from macrophages from tumor-bearing mice has been shown to suppress LAK activity by Parhar et al., Prostaglandin E.sub.2 -mediated inactivation of various killer lineage cells by tumor bearing host macrophages, J. Leuk. Biol. 44:474-484, 1988. PGE.sub.2 also down-regulates IL-2 receptors, blocks IL-2 production, and induces suppressor cells as shown by Parhar et al, supra; Lala et al., Cure of B16F10 melanoma lung metastasis in mice by chronic indomethacin therapy combined with repeated rounds of interleukin-2: characteristics of killer cells generate in situ, Cancer Res. 48:1072-1079, 1988; Rappaport et al., Prostaglandin E.sub.2 inhibits the production of human interleukin-2, J. Exp. Med. 155:943-948, 1982; Rogers et al., Suppression of B-cell and T-cell responses by the prostaglandin synthesis-dependent suppressor (PITS), Cell Immunol. 66:269, 1982. Indomethacin, a specific inhibitor of cyclooxygenase has been shown to enhance LAK generation and IL-2 antitumor activity in mice by Lala, et al. supra. However, cyclooxygenase inhibitors, such as indomethacin and ibuprofen, have not been shown to modify tumor or immune responses in cancer patients receiving IL-2 therapy, as described in Sosman et al., Repetitive weekly cycles of interleukin-2. II. Clinical and immunologic effects of dose, schedule, and addition of indomethacin. J. Natl. Cancer Inst. 80:1451-1461, 1988; Eberlein et al., Ibuprofen causes reduced toxic effects of interleukin-2 administration in patients with metastatic cancer; Arch. Surg. 124:542-547, 1989. Reactive oxygen species ROS, such as superoxide anion (O.sub.2.sup.-), have been shown to inhibit NK activity by Seaman et al., Suppression of natural killing in vitro by monocytes and polymorphonuclear leukocytes. Requirements of reactive metabolites of oxygen. J. Clin. Invest. 69:876-888, 1982 and Lipsky, Immunosuppression by D-penicillamine in vitro:inhibition of human T lymphocyte proliferation by copper-or ceruloplasmin- dependent generation of hydrogen peroxide and protection by monocytes. J. Clin. Invest. 73:53-65, 1984. However, the effects of ROS on LAK cytotoxicity and whether ROS scavengers improve IL-2 antitumor activity in vivo have not been established. It is to be noted that patients responding to IL-2/LAK therapy had higher base-line levels of the ROS scavenger, ascorbic acid, and recovered more rapidly from IL-2 induced depletion of ascorbic acid than did non-responders, as described in Marcus et al., Severe hypovitaminoisis C occurring as the result of adoptive immunotherapy with high dose interleukin-2 and lymphokine activated killer cells. Cancer Res. 47:4028-4212, 1987.
Aci-reductone compounds are a family of synthetic compounds that contain the moiety: --C(OH).dbd.C(OH)--C.dbd.O and are discussed in Witiak et al., Hypocholesterolemic and aggregatory properties of 2-hydroxytetronic acid redox analogues and their relation to clofibric acid. J. Med. Chem. 25:90-93, 1982; Witiak et al., Synthetic aci-reductones: 3,4-dihydroxy-2H-1-benzopyran-2-ones and their cis and trans 4a, 5, 6, 7, 8, 8a-hexahydro diastersomers. Antiaggregatory, antilipemic, and redox properties compared to those of the 4-substituted 2-hydroxytetronic acids, J. Med. Chem. 31:1437-1445, 1988; and Witiak et al., Comparative antiaggregatory activity in human platelets of a benzopyranone aci-reductone, clofibric acid, and 2,3-dihydrobenzofuran analogue. J. Med. Chem. 29:2170-2174, 1986. Possessing the same redox functionality found in ascorbic acid, aci-reductones can function as scavengers of ROS in vivo. In addition, aci-reductone compounds can also inhibit oxidizing enzymes involved in AA metabolism by serving as alkyl and aryl carboxylic acid mimics at the metal containing active sites.
It is shown herein that due to their capacity to affect both AA and ROS metabolism the aci-reductone compounds can improve IL-2-induced LAK generation.